Fuel injection valve

ABSTRACT

A fuel injector ( 1 ), especially an injector for fuel injection systems of internal combustion engines ( 51 ), has a piezoelectric or magnetostrictive actuator ( 14 ), a valve-closure member ( 8 ) that is actuated by an actuator ( 14 ) using a valve needle ( 9 ), the valve-closure member cooperating with a valve seat surface ( 7 ) to form a sealing seat, and having at least one spray-discharge opening ( 10, 11 ) that is sealed by the sealing seat. In this context, the valve seat surface ( 7 ) and/or the valve-closure member ( 8 ) has partial areas ( 30   a,    30   b ) that are arranged so as to be offset on the circumference, the partial areas throttling a fuel flow to differing extents as a function of a stroke of the valve needle ( 9 ).

FIELD OF THE INVENTION

The present invention relates to a fuel injector.

BACKGROUND INFORMATION

German Published Patent Application No. 40 05 455 describes a fuelinjector that includes a piezoelectric actuator and a valve-closuremember that can be actuated by a valve needle, the valve-closure membercooperating with a valve seat surface to form a sealing seat. Thevalve-closure member contacts an annular sealing point on the valve seatsurface, as a result of which a spray-discharge opening is sealed. Whenthe actuator is actuated, the valve-closure member lifts off from thevalve seat surface, as a result of which the sealing seat is opened andfuel is spray-discharged from the fuel injector. In this context, theflow of spray-discharged fuel is rotationally symmetrical with respectto a valve axis. Thus the fuel is spray-discharged in a rotationallysymmetrical spray cone.

One disadvantage in the fuel injector described in German PublishedPatent Application No. 40 05 455 is that it is not possible to specify adirectional distribution of the spray-discharged fuel. As a result, itis impossible in the known fuel injector to achieve a controllednon-homogeneous fuel distribution in the combustion chamber of aninternal combustion engine.

In German Published Patent Application No. 44 34 892, a fuel injector isdescribed that has two spray-discharge openings situated at varyinglevels with respect to a valve axis. In this manner, the fuel isspray-discharged in two discharge directions, which include varyingangles with respect to the valve axis.

One disadvantage in the fuel injector described in German PublishedPatent Application No. 44 34 892 is that the two spray-dischargedirections are fixedly prescribed by the design. In addition, therelationship of the fuel streams flowing through the two spray-dischargeopenings is prescribed by the design and cannot be controlled,especially during the operation of the fuel injector.

SUMMARY OF THE INVENTION

In contrast, the fuel injector according to the present invention hasthe advantage that it is possible to control the fuel streams of fueljets emerging in different spray-discharge directions, and theirrelationship to each other.

It is advantageous if, for throttling the fuel, partial areas areprovided directly at the spray-discharge opening so as to be offset onthe periphery of the valve seat surface and/or the valve-closure member.In this manner, particularly effective throttling is provided.

In addition, it is advantageous if a partial area has a raised areaconfigured on the valve seat surface and/or on the valve-closure member.As a result, when the sealing seat is opened by a first stroke of thevalve needle, the fuel flow in the fuel jet throttled by the raised areais powerfully throttled in comparison to the unthrottled fuel jet. Whenthe sealing seat is opened by a second, larger stroke of the valveneedle, the throttle effect generated by the raised area is reduced, asa result of which the fuel flow of the throttled fuel jet adjusts to thefuel flow of the unthrottled fuel jet.

It is also advantageous if the valve-closure member, for the purpose ofcreating an interstitial space, tapers to a blunter end than the valveseat surface, so that interstitial space, with the exception of thethrottling partial areas, essentially widens radially. In this way, inresponse to a small stroke of the valve needle, a larger fuel flow isachieved, as result of which the difference between the throttled andthe unthrottled fuel jets increases.

It is also advantageous if the valve-closure member contacts a sealingpoint on the valve seat when the fuel injector is closed, the sealingpoint being configured, with respect to the direction of flow, eitherdownstream or upstream of the throttling partial areas, it beingespecially advantageous if the sealing surface is situated essentiallyin a plane oriented perpendicular to a valve axis. As a result, thesealing effect is not achieved on the throttling partial areas; inparticular, when the fuel injector is closed, the valve-closure memberin the partial areas does not contact the valve seat surface, as aresult of which a reliable closing of the valve is assured. In addition,the sealing surface is easy to realize in this manner.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts an axial section of an exemplary embodiment of a fuelinjector according to the present invention.

FIG. 2 depicts the detail designated as II in FIG. 1 in the closed stateof the fuel injector.

FIG. 3 depicts the detail designated as II in FIG. 1 in response to afirst stroke of the valve needle.

FIG. 4 depicts the detail designated as II in FIG. 1 in response to asecond, larger stroke of the valve needle.

FIG. 5 depicts the detail designated as II in FIG. 1 in an alternativeembodiment.

FIG. 6 depicts a detail of a fuel injector according to the presentinvention in accordance with a further exemplary embodiment.

FIG. 7 depicts a detail of a fuel injector according to the presentinvention in accordance with a further exemplary embodiment.

FIG. 8 depicts an application example of the fuel injector according tothe present invention.

DETAILED DESCRIPTION

FIG. 1 depicts, in a partial axial cutaway representation, a fuelinjector 1 according to the present invention. Fuel injector 1 is usedespecially for directly injecting fuel, especially gasoline, into acombustion chamber of a mixture-compressing, spark-ignited internalcombustion engine, as a so-called gasoline direct injector. However,fuel injector 1 according to the present invention is also suited forother application cases.

Fuel injector 1 has a valve housing 2, which is joined to a fuel intakefeed pipe 3, valve housing 2 and fuel intake feed pipe 3 beingsurrounded in one segment by a plastic element 4. On plastic element 4,an electrical terminal 5 is configured, which can connect an electricalsupply line to fuel injector 1. On valve housing 2, a valve seat body 6is mounted, which has a valve seat surface 7, which cooperates with avalve-closure member 8 to form a sealing seat. Valve-closure member 8 isconfigured as a truncated cone tapering in the spray-dischargedirection. In this configuration, fuel injector 1 is executed as aninward-opening fuel injector 1. Valve-closure member 8 is actuated by avalve needle 9, which in the depicted exemplary embodiment is configuredas a single piece including valve-closure member 8. Valve seat body 6has spray-discharge openings 10, 11, through which the fuel isspray-discharged from fuel injector 1.

Valve needle 9 has a cylindrical segment 12, which is connected to atubular sleeve 13. Sleeve 13 is surrounded over one segment by apiezoelectric or magnetostrictive actuator 14, a collar 15 of sleeve 13gripping actuator 14 from behind. Actuator 14 is supported, on the onehand, on valve housing 2, and, on the other hand, on collar 15 of sleeve13. Using a compression spring 16, which acts upon collar 15 of sleeve13, actuator 14 is biased. In this context, compression spring 16 issupported on a stop face 17, which is configured on fuel intake feedpipe 3. In order to permit the fuel to flow through, sleeve 13 hascavities 18 a, 18 b.

To actuate fuel injector 1, actuator 14 is acted upon by an electricalcontrol signal, as result of which the actuator expands in opposition tothe force of compression spring 16 and sleeve 13 moves in the directionof fuel intake feed pipe 3. In this manner, valve-closure member 8 ofvalve needle 9 is lifted off from valve seat surface 7 of valve seatbody 6, as result of which the sealing seat formed by valve-closuremember 8 and valve seat surface 7 is opened. Fuel travels intospray-discharge opening 10, 11 through the gap that arises betweenvalve-closure member 8 and valve seat surface 7, as result of which thefuel is spray-discharged from fuel injector 1. In this context, fuel issupplied from fuel intake feed pipe 3 through an interior cavity 19 infuel intake feed pipe 3, a compression spring space 20, an interiorcavity 21 of tubular sleeve 13, and cavities 18 a, 18 b, into a fuelchamber 22. Via an interstitial space 23 formed between valve needle 9and valve seat body 6, fuel is supplied from fuel chamber 22 to thesealing seat formed by valve-closure member 8 and valve seat surface 7.Interstitial space 23 can be created, e.g., by grooves configured onvalve needle 9 or valve seat support 6.

Valve seat surface 7 and/or valve-closure member 8 on their peripherieshave partial areas arranged so as to be offset, the partial areasthrottling a fuel flow to different extents as a function of a stroke ofvalve needle 9. This can be seen in the detail shown in FIGS. 2 through7. In this context, FIGS. 2 through 5 depict different embodiments ofthe section designated as II in FIG. 1, and FIGS. 6 and 7 depict furtherembodiments for an outward-opening fuel injector. Elements alreadydescribed are provided with corresponding reference numerals, so that norepeated description is necessary.

In the exemplary embodiment depicted in FIG. 2, valve seat body 6 hasdifferent partial areas 30 a and 30 b. In this context, valve-closuremember 8, for the purpose of creating an interstitial space 31, tapersto a blunter end than valve seat surface 7, so that interstitial space31, with the exception of partial area 30 a, widens radially towardvalve axis 34. To assure a reliable closing of fuel injector 1, partialareas 30 a, 30 b do not contact valve-closure member 8. At a circularsealing point 32, valve-closure member 8 contacts valve seat surface 7of valve seat body 6, the sealing point being configured, with respectto a direction of flow 33, upstream of partial areas 30 a, 30 b. In thiscontext, sealing point 32 is situated on a plane essentially orientedperpendicular to valve axis 34. Partial area 30 a has a raised area 35configured on valve seat surface 7. In this context, raised area 35, andpartial area 30 a, are provided directly at spray-discharge opening 11.

In FIG. 3, valve-closure member 8 of valve needle 9 is actuated by afirst stroke of valve needle 9. In this manner, fuel travels intointerstitial space 31, from which it is spray-discharged throughspray-discharge opening 10. A first fuel jet 40 is generated by the fuelflowing through spray-discharge opening 10. In addition, fuel travelsinto spray-discharge opening 11, as result of which a flow of fuel isgenerated through spray-discharge opening 11, creating a second fuel jet41. As a result of raised area 35 in partial area 30 a, the fuel flowthrough spray-discharge opening 11 is throttled to greater extent thanthe fuel flow through spray-discharge opening 10, as result of whichfuel jet 41 is configured so as to be significantly smaller than fueljet 40. Therefore, more fuel is spray-discharged through spray-dischargeopening 10 than through spray-discharge opening 11.

In FIG. 4, valve-closure member 8 is actuated by a second stroke ofvalve needle 9, this stroke being greater than the first valve needlestroke. Valve-closure member 8 as a result distinctly lifts off fromvalve seat surface 7 also in partial area 30 a, as a result of which thethrottle effect of raised area 35 is reduced. Therefore, the fuel flowthrough spray-discharge opening 11 is comparable to the fuel flowthrough spray-discharge opening 10, as a result of which two comparablefuel jets 40, 41 are created. Therefore, the result is a spray-dischargeof fuel from fuel injector 1 that is essentially symmetrical withrespect to valve axis 34.

Since the variable stroke of valve needle 9 can be adjusted usingpiezoelectric or magnetostrictive actuator 14, a range of intermediatesettings of the application cases depicted in FIGS. 2, 3, and 4 can beachieved. Therefore, by varying fuel jets 40, 41, the fuel quantitydistribution of fuel injector 1 can be varied in a controlled mannerduring operation.

In FIG. 5, a further embodiment of fuel injector 1 according to thepresent invention is depicted. In this exemplary embodiment,valve-closure member 8 has a partial area 30 a including a raised area42. Valve seat surface 7 of valve seat body 6 is essentially configuredso as to be conical. In partial area 30 a, spray-discharge opening 11 isthrottled, the variable throttling being achieved as a function of astroke of valve needle 9. In this manner, spray-discharge openings 10,11 are throttled to different extents, as a result of which a fuelquantity distribution of fuel injector 1, described in FIGS. 2 through4, can be varied in a controlled manner.

FIG. 6 depicts an exemplary embodiment for an outward-opening fuelinjector 1. Valve-closure member 8 is configured so as to widen in thespray-discharge direction. Valve seat surface 7 has a partial area 30 a,in which a raised area 42 is configured on valve seat surface 7 of valveseat body 6. The fuel injector has a spray-discharge opening 10, whichis divided into a first spray-discharge area 43 and a secondspray-discharge area 44. In this context, first spray-discharge area 43is throttled by partial area 30 a to a different extent than secondspray-discharge area 44. Valve-closure member 8, for creatinginterstitial space 31, is configured so as to be blunter than valve seatsurface 7, so that interstitial space 31 broadens radially in thedirection of flow. Valve-closure member 8 contacts a sealing point 32 onvalve seat surface 7, the sealing point, with respect to flow direction33, being configured downstream of partial areas 30 a and 30 b and beingsituated essentially in a plane that is oriented perpendicular to valveaxis 34.

In response to a stroke of valve needle 9, the fuel flow in secondspray-discharge area 44 is initially greater than the fuel flow in firstspray-discharge area 43. As the stroke of valve needle 9 isprogressively increased, the influence of partial area 30 a on thethrottling of the fuel jet spray-discharged in first spray-dischargearea 43 is decreased. As a result, the fuel flow in firstspray-discharge area 43 is increasingly adjusted to the fuel flow insecond spray-discharge area 44. Therefore, as a result of the stroke ofvalve needle 9, the fuel quantity distribution of the fuelspray-discharged from a fuel injector 1 can be controlled.

FIG. 7 depicts a further exemplary embodiment for an outward-openingfuel injector 1. In this exemplary embodiment, valve-closure member 8has a partial area 30 a, in which a raised area 42 is configured onvalve-closure member 8. As a result, in a similar way to that describedin FIG. 6, in spray-discharge areas 43, 44, the flow of fuelspray-discharged from fuel injector 1 is throttled to different extents.

FIG. 8 depicts an application example in which fuel injector 1 accordingto the present invention is used for directly injecting fuel, especiallygasoline, into combustion chamber 50 of an internal combustion engine51. In the application example, fuel injector 1 has six spray-dischargeopenings arranged so as to be offset on the circumference. In addition,the valve seat surface and/or the valve-closure member according to thepresent invention have partial areas that are arranged so as to beoffset on the circumference, the partial areas throttling the fuel flowto different extents as a function of a stroke of the valve needle. Fuelinjector 1 is joined to cylinder 52 of internal combustion engine 51, apiston 53 being guided in cylinder 52 in a movable fashion. In acylinder head 54, a spark plug 55 is mounted. When fuel injector 1 isactuated, fuel jets 56 a through 56 f emerge through the spray-dischargeopenings. In this context, the fuel flows of fuel jets 56 a through 56 cand those of fuel jets 56 d through 56 f are, in each case, throttled atleast roughly to the same extent, the fuel flows of fuel jets 56 athrough 56 c being throttled to different extent than the fuel flows offuel jets 56 d through 56 f. In this context, the throttling is executedso that in response to a first valve needle stroke of fuel injector 1,fuel jets 56 d through 56 f are throttled more strongly than fuel jets56 a through 56 c, so that the injection of fuel into combustion chamber50 is essentially carried out in the area of spark plug 55. In responseto a second, larger valve needle stroke of fuel injector 1, the fuelflows of fuel jets 56 a through 56 f are approximately equal, so thatthe fuel is distributed uniformly in combustion chamber 50 of internalcombustion engine 51. In this manner, even in the very lean operation ofinternal combustion engine 51, an effective ignition of the injectedfuel can be achieved. On the basis of the variable fuel quantitydistribution, it is possible to react more effectively to the differentdemands of internal combustion engine 51, such as homogeneousoperation/layered operation, cold start, full load/partial load.

Partial areas 30 a, 30 b, raised to varying extents in the differentexemplary embodiments described, are formed, e.g., by stamping.

The present invention is not limited to the exemplary embodimentsdescribed. In particular, in the exemplary embodiments only theprinciple of variable throttling of the fuel flow is described.Therefore, the present invention is suited for any number ofspray-discharge openings 10, 11, and for any configuration of them. Inaddition, the different throttling actions can also be achieved throughsuitable cavities in valve-closure member 8 or valve seat body 6.

What is claimed is:
 1. A fuel injector, comprising: one of apiezoelectric actuator and a magnetostrictive actuator; a valve needle;a valve-closure member capable of being actuated by the one of thepiezoelectric actuator and the magnetostrictive actuator in accordancewith an operation of the valve needle; and a valve seat surfaceincluding at least two spray-discharge openings, the valve-closuremember configured to cooperate with the valve seat surface to form asealing seat that seals the at least two spray-discharge openings,wherein: at least one of the valve seat surface and the valve-closuremember includes partial areas that are arranged so as to be offset on acircumference, and the partial areas throttle a fuel flow to differingextents through the spray-discharge openings as a function of a strokeof the valve needle.
 2. The fuel injector according to claim 1, wherein:the fuel injector is for a fuel injection system of an internalcombustion engine.
 3. The fuel injector according to claim 1, wherein:at least one of the partial areas is arranged directly at one of thespray-discharge openings.
 4. The fuel injector according to claim 1,wherein: the fuel flow is throttled to differing extents at at least twoof the spray-discharge openings.
 5. The fuel injector according to claim1, wherein: at least one of the partial areas includes a raised areathat is configured on at least one of the valve seat surface and thevalve-closure member.
 6. The fuel injector according to claim 1,wherein: in order to create an interstitial space, the valve-closuremember tapers to a blunter end than the valve seat surface so that theinterstitial space widens radially in a direction of flow.
 7. The fuelinjector according to claim 1, wherein: when the fuel injector isclosed, the valve-closure member contacts a sealing point on the valveseat surface, and the sealing point is configured, with respect to adirection of flow, at a position that is one of downstream and upstreamof the partial areas.
 8. The fuel injector according to claim 7,wherein: the sealing point is situated essentially in a plane that isoriented perpendicular to a valve axis.
 9. A fuel injector, comprising:one of a piezoelectric actuator and a magnetostrictive actuator; a valveneedle; a valve-closure member capable of being actuated by the one ofthe piezoelectric actuator and the magnetostrictive actuator inaccordance with an operation of the valve needle; and a valve seatsurface with which the valve-closure member cooperates to form a sealingseat that seals a spray-discharge opening; wherein at least one of thevalve seat surface and the valve-closure member includes partial areasthat are arranged so as to be offset on a circumference; wherein thepartial areas throttle a fuel flow to differing extents as a function ofa stroke of the valve needle; and wherein the valve-closure member isarranged to contact a sealing point of the valve seat surface in aclosed position of the fuel injector, the sealing point arranged, withrespect to a direction of flow, at a position downstream of the partialareas.